The 22-year-old, ranked 96th in the world, had a wobble in the second set but recovered impressively to triumph 6-3 1-6 6-3 and set up a meeting with second seed Andreas Seppi tomorrow.
Paire, who is bidding to become the first maiden winner of the season, told www.atpworldtour.com: "It was a tough match. Andujar is a really good player.
"For me, the first set was very good. After I was a bit tired. But in my head I was thinking, at one-set all, I could win if I played my best. It's my first ATP final. For me, it's unbelievable."
Seppi got off to a slow start in his clash with David Nalbandian on Saturday and then had to fight back from a break down in the decider, eventually prevailing 2-6 6-2 7-5.